Hi,
Sorry for the late reply. Applying the autocomplete solution will not preload anything and shouldn’t put any extra strain on your server (or prolong the form load) as not query are run before the user starts typing into the field.

When this is said, you can put the function call in a separate function and call it whenever you are ready. You cannot call it with parameters from a DFFS rule, but you can wrap each call (to customer or supplier) in separate functions an call these functions from DFFS rules. Here is an example: